Transfer line chemicals coking process



Sept. 8,1959 w. J. MEITRAILER 2,903,416

TRANSFER LINE CHEMICALS COKING PROCESS Filed June 26, 1956 CONVERSIONPRODUCT CYCLONE I l TRANSFER LINE REACTOR STRlPPER William J. Me'rmilerInvenfo'r By a6 a. Attorney'- intermediates.

TRANSFER LINE CHEMICALS COKING PROCESS WilliamJoseph Metrailer,Baton-Rouge, 1a., assignorto EssoResearchand Engineering Company, acorpora= .tion of Delaware Application 'June' 26, 1956, Serial No.594,031

'4 Claims. (Cl. 208--127) This invention relates to a transfer line,residua coking process for the production of chemicals and chemical Itis more particularly concerned with the conversion ofheavy'hydrocarbonoils by contact with highly heated solids flowing through an elongated,narrowly confinedconversion zone, to predominantly coke, low molecularweight, normally gaseous, unsaturated hydrocanbons and aromatic,unsaturated, lo-w'boiling, normally liquid hydrocarbons.

1 here has been an increasing'demand for low molecu- .1 ar weight,normally gaseous, unsaturated hydrocarbons such as (ethylene, propyleneand butadiene.

mixtures thereof. Typically, such .feeds have an initial boilingpointabove about 700 F., an API gravity of about"" to20, and 'aConradson carbon residue content of about 5 'to 40 wt. percent (see ASTMtest D-l89-4l).

One method of "coking such heavy oils has been to contact the oils withsolids at a temperature above 1200 F. in what has been termed a transferline reaction zone. The solids are passed rapidly through the transferline zone, and the injected residual oil, upon contact with the solids,undergoes pyrolysis-depositing coke on the solids and evolving lighterhydrocarbon products.

One of the troubles associated with this type of operation has beenobtaining good distribution of the injected residual oil on the solids.The contact times in such a transfer line operation are usually belowabout 5 seconds, contact times beyond this resulting in poor productdistributions and yields. With such a short contact time, it isdifficult to assure good contacting of the liquid viscous oil feed andthe highly heated solids. Besides a loss in coking eificiency,maldistribution of the feed often results in coking of the equipment ator near the point of feed injection.

This invention provides an improved method for coking residual oils in atransfer line system, with special provision for assuring proper feeddistribution. This improved method comprises first premixing the feedwith flowing, relatively cool, particulate solids, recovered from thetransfer line reaction zone effiuent, so that the temperature of theresulting mixture is subtantially below, i.e., 50 to 500 F. below thereaction zone temperature. This lower temperature permits longercontacting times to be realized and thus adequate and uniformdistribution of the feed on the solids can be obtained. After obtaininggood distribution of the liquid feed on the cool solids, the temperatureof the admixture is raised to the desired reaction temperature by theinjection of freshly heated solids.

It will be appreciated by those skilled in the art that with heavyresidua boiling predominately above 900 F., this problem of feeddistribution is most acute. With United States Patent P 2,903,416Patented Sept. 8, 1959 lighter materials, such as gas oils, that arereadily vaporizable, the problem of feed distribution rarely occurs.

This-invention will be better understood by the following description ofthe drawing attached to and forming a part of this specification.

The drawing illustrates a transfer line reactor conversion systemcomprising a transfer line reactor 10, a cyclone or'solids'separatin gsystem 11, and-a-stripping zoneand solids reservoir or holdup chamber12. The conversion products and entrained solids issuing from reactor 10are separated 'in cyclone 11, the separated solids being passedby line13 to the stripping zone. The conversion products are removed overheadfrom cyclone 11 by line 14. A quench medium, preferably a liquid, isinjected into the conversion products'by line 15.

The solids separted in cyclone 11 areretained in the stripper 12 topermit further cracking of any heavy hydrocarbonaceous material retainedin the solids. These secondary conversion products are removed from thestripper by line 16. Becausea-seal must be maintained betweencyclone lland stripper 12, it is desirable in many cases to either pass thesecondary conversion-products by lines 16 and 17 to line 14before'thequench point, or by line 18 to the inlet of the cyclone.Thisarrangeinent stabilizes theseal between the vessels so that it doesnot changewith changesin-the pressure drop across'the quench point.

Steam or otherfl'uidizing or stripping gas can be admitted to the baseof vessel 12 by line 19.

Aportion of the solids in stripper '12 is passed [by line 20 to anexternal heating means or system not shown. This heating means maycomprise a burner such as a fluid bed oratransfer line burnerforconsurninga portion of the coke deposited on the circulatingsolids.In cases where the value of the coke is greater than other extraneousliquid or gaseous fuels, the latter may be burned to supply part or allof'the heat required. The solids are heated to a temperature to 400 F.above the desired chemicals coking temperature. The solids so heated arereturned to the base of reactor 10 by line 21, being conveyed bysuitable conveying gas such as steam, nitrogen, CO etc.

According to this invention, the heavy viscous residual oil feed isinjected into the reactor 10 by premixing it with relatively coolerflowing solids in a riser 22. The cooler solids are withdrawn fromstripper 12 by line 22 and circulated to the feed injection point bymeans of a suitable riser or conveying gas such as steam, CO lighthydrocarbons, etc. Relatively dense phase conditions are maintained inthe riser such that the feed injected by line 23 has a sufiicient amountof solids available upon which to be distributed, and the density of thesolids is such as to prevent undue contacting of the fresh feed with theriser walls. Because the temperature of the resulting admixture issubstantially below the chemicals coking temperature, preferably atleast 50 F. below, more time is permitted in the riser for the naturalagitation and mixing of the fluidized particles to properly distributethe feed. Contact times in the range of 0.1 to 5 seconds are ordinarilyrealized in the riser before the heated solids are injected.

After permitting adequate time for distribution of the feed, the heatedsolids from line 21 are mixed with the contents of line 22 to raise thetemperature thereof above 1200 F. The resulting mixture is then rapidlyflowed through reactor 10 to cyclone 11. The conversion products arequenched with the quench medium supplied by line 15, preferably to below700 F., within 0.1 to 5.0 seconds after the heated solids are mixed withthe contents of line 22. This quench can comprise liquids, e.g., wateror cooled oils; solids, e.g., cooled coke particles; or gases, e.g.,cooled light hydrocarbons or steam. The conversion products, afterquenching, are subjected to further processing to recover the desiredproducts. This further processing can include by way ofillustration-fractionation, absorption, crystallization, extraction,extractive or azeotropic distillation, and polymerization.

The following table, with reference to the drawing, summarizes thepertinent operating conditions and presents a specific example thereof.

Operatzng condztzons Preferred Example 1 Range Riser 22:

Temp. before feed injection, F 1,200 to 1,600 1, 400 Density before feedinjection, lbs/cu. ft.. 10 to 45 30 Riser gas superficial velocity,before feed 1 to 20 3 injection, ft./sec. Residua feed injection,lbs/lb. solids 0.1 to 0.4 0. 2

circulated. Temp, after feed injection, F 000 to 1,200. 1,100 Feedcontact time in riser, sec 0.1 to 5.0 1.0 Transfer Line Reactor 10:

Temp. of Added Solids, F Above 1,300." 1, 600 AHiJIIlIO -ILI JJE ofadded solids, percent of total Above 70 80 Temp. after addition ofsolids, F 1,200 to 1,600. 1, 400 Detnsity after addition of solids,lbs/cu. 0.5 to 4 1 Riser gas superficial velocity, after addi- 25 to 60.2 45

tion of solids, ft./sec. Average feed residence time before 0.1 to 5.00. 25

quench, see. Pressure at cyclone outlet, p.s.i.a 5 to 35 25 1 Based onthe contact solid comprising particulate coke produced by the processunder 1000 microns in size, 200 microns average size, and using aHawkins residuum having an I.B.P. of 900 F Having described thisinvention, what is sought to be protected by Letters Patent issuccinctly set forth in the following claims.

What is claimed is:

1. In a coking process for converting heavy hydrocarbon oils boilingpredominantly above 900 F. to lighter hydrocarbon products by contactwith a dispersed suspension of particulate solids at a cokingtemperature in the range of 1200 to 1600 F. in a transfer line reactionzone, the improvement which comprises mixing said oil in an amount inthe range of 0.1 to 0.4 lb./lb. with flowing particulate solidsrecovered from the transfer line reaction zone efiluent to form a densephase suspension in a riser, the temperature of the resulting mixturebeing from to 500 F. below said coking temperature in said transfer linereaction zone, and thereafter adding freshly heated solids having atemperature above 1300 F. to said mixture without separating saidinitially mixed solids from said mixture to raise the temperature of theresulting mixture to said coking temperature of about 1200 F.-1600 F.and passing the thus heated mixture as a dispersed suspension throughsaid transfer line reaction zone.

2. Process of claim 1 wherein said mixture is maintained in the riserfor a time in the range of 0.1 to 5 seconds, and said heated mixture ismaintained at coking temperature for a time less than 5 seconds.

3. The process of claim 1 wherein said lighter hydrocarbon products areseparated from the solids issuing from said transfer line reaction zone,the solids so separated are received and retained in a stripping zone,and a portion of the solids from the stripping zone is directly mixedwith the heavy hydrocarbon oil feed in the riser and the remainder ofthe solids is circulated through a heating zone to supply said freshlyheated solids.

4. Process of claim 1 wherein the solids initially mixed with said heavyhydrocarbon oil feed amount to less than 30% of the solids passedthrough said transfer line reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS2,731,508 Jahnig et al. Jan. 17, 1956 2,734,853 Smith et al. Feb. 14,1956 2,735,804 Boston et al. Feb. 21, 1956 2,737,479 Nicholson Mar. 6,1956 2,813,916 Boston Nov. 19, 1957

1. IN A COKING PROCESS FOR CONVERTING HEAVY HYDROCARBON OILS BOILINGPREDOMINANTLY ABOVE 900*F. TO LIGHTER HYDROCARBON PRODUCTS BY CONTACTWITH A DISPERSED SUSPENSION OF PARTICULATE SOLIDS AT A COKINGTEMPERATURE IN THE RANGE OF 1200* TO 1600*F. IN A TRANSFER LINE REACTIONZONE, THE IMPROVEMENT WHICH COMPRISES MIXING SAID OIL IN AN AMOUNT INTHE RANGE OF 0.1 TO 0.4 LB./LB. WITH FLOWING PARTICULATE SOLIDSRECOVERED FROM THE TRANSFER LINE REACTION ZONE EFFLUENT TO FORM A DENSEPAHSE SUSPENSION IN A RISER, THE TEMPERATURE OF THE RESULTING MIXTUREBEING FROM 50* TO 500*F. BELOW SAID COKING TEMPERATURE IN SAID TRANSFERLINE REACTION ZONE, AND THEREAFER ADDING FRESHLY HEATED SOLIDS HAVING ATEMPERATURE ABOVE 1300*F. TO SAID MIXTURE WITHOUT SEPARATING SAIDINITIALLY